This specification relates to scoring documents responsive to search queries.
Internet search engines provide information about Internet accessible documents (e.g., web pages, images, text documents, multimedia content) that are responsive to a user's search query by returning a set of search results in response to the query. A search result can include, for example, a Uniform Resource Locator (URL) and a snippet of information for each of a number of documents responsive to a query. The search results can be ranked, i.e., placed in an order, according to scores assigned to the search results by a scoring function or process.
The scoring function value for a given document is derived from various indicators, for example, where, and how often, query terms appear in the given document, how common the query terms are in the documents indexed by the search engine, or a query-independent measure of quality of the document itself. Some scoring functions alternatively, or additionally, use quality of result statistics for pairs of queries and documents. These quality of result statistics can be derived from indicators that describe past user behavior. For example, a quality of result statistic for a given document and a given query can be derived from how frequently a user selected a search result corresponding to the given document when the search result was presented on a search results page for the given query.